As technology nodes shrink, in some integrated circuit designs, replacing the polysilicon gate electrode with a metal gate electrode can improve device performance with the decreased feature sizes. Providing metal gate structures (e.g., including a metal gate electrode rather than polysilicon) offers one solution. One process of forming a metal gate stack is termed a “gate last” process in which the final gate stack is fabricated “last” which allows for a reduced number of subsequent processes, including high temperature processing, that are performed before formation of the gate stack. Additionally, as the dimensions of transistors decrease, the thickness of the gate oxide may be reduced to maintain performance with the decreased gate length. In order to reduce gate leakage, high dielectric constant (high-k or HK) gate insulator layers are also used which allows to maintain the same effective thickness as would be provided by a typical gate oxide used in larger technology nodes.